There have been developed and manufactured various types of optical pickup systems capable of conducting reproducing and recording of information for a plurality of optical information recording media such as CD and DVD, and they have become widespread in general. As an optical pickup apparatus of this kind, there exist, for example, those each converging light fluxes emitted from a pair of light sources each having a different wavelength onto a pair of information recording media each being different from others (see Patent Document 1). In this optical pickup apparatus, a diffractive optical surface is formed on any one of optical elements on an optical path, and a difference of the diffraction orders is utilized to conduct recording and reproducing of information with the same working distance for different information recording media each having a protective substrate with a different thickness.
Further, there exist optical information recording media of types to record information by using holography. Each of the optical information recording media has a recording layer for hologram recording; and a reflection layer formed immediately under the recording layer and including a positioning mark for a hologram recording area (see Patent Document 2). In this information recording medium, it is possible to attain speeding up of information reproducing or the like, because information is recorded and reproduced simultaneously with positioning by using the mark formed on the reflection layer.
Patent Document 1: TOKUKAI No. 2003-66324
Patent Document 2: TOKUKAI No. 2004-158113
However, a diffractive optical surface formed in the former causes considerable light loss is on the diffractive optical surface, and increases a cost of a light-converging optical system.
Further, when a positioning mark is provided as in the latter, it is ordinarily considered to set detecting light for the mark and recording light for hologram to have different wavelengths each other. In other words, it is necessary to detect the focal points with a different wavelengths because it is hard to adjust the focal point using with light for recording and reproducing of hologram, resulting in the necessity to make working distances respectively for both wavelengths agree each other.